Web feeding apparatus for blank making machine

ABSTRACT

A machine for making box blanks or the like from a continuous strip or web of sheet material includes an unwind stand having a large diameter parent roll of the material from which a web or strip is cut and delivered to power unwind rolls. The unwind rolls feed material into a cylindrical vacuum box having adjustable side sealing plates, in which a loop of the material is formed with the assistance of a suction blower. Index or oscillating draw rolls intermittently remove the web material from the vacuum box for action by a reciprocating die set that forms the blanks when the web is not moving. The vacuum box is provided with a bank of photo resistant cells on one side of the loop and a bank of lamps on the other side, sensing the height of the loop and for controlling a variable DC speed motor that drives the unwind rolls, using an S.C.R. type control. The photocell control maintains the loop in the vacuum box at a nominal length and the inertia of the unwind drive system and the mechanism that feeds web to the loop is such that the feed motor does not respond to the rapid intermittent variations in loop length resulting from indexing of the draw rolls. A loop size sensing switch controls the initial size of the loop when starting up the machine. In one form of the apparatus a flexible opaque shade rides inside the loop so that the photocell control can operate on transparent web material.

United States Patent Eggert [11] 3,807,612 [451 Apr. 30, 1974 WEBFEEDING APPARATUS FOR BLANK MAKING MACHINE [75] Inventor: Ralph H.Eggert, Cinnaminson, NJ.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: May 15, 1973 [21] Appl. No.: 360,520

[52] US. Cl 226/42, 226/118, 226/97, 226/111, 226/117, 242/183 [51] Int.Cl B65h 23/22 [58] Field of Search 226/97, 113, 42,118, 111, 226/117;242/183, 184

Primary Examiner-Allen N. Knowles Attorney, Agent, or FirmC. E. Tripp[57] ABSTRACT A machine for making box blanks or the like from a PARENTROLL,R

continuous strip or web of sheet material includes an unwind standhaving a large diameter parent roll of the material from which a web orstrip is cut and delivered to power unwind rolls. The unwind rolls feedmaterial into a cylindrical vacuum box having adjustable side sealingplates, in which a loop of the material is formed with the assistance ofa suction blower. Index or oscillating draw rolls intermittently removethe web material from the vacuum box for action by a reciprocating dieset that forms the blanks when the web is not moving. The vacuum box isprovided with a bank of photo resistant cells on one side of the loopand a bank of lamps on the other side, sensing the height of the loopand for controlling a variable DC speed motor that drives the unwindrolls, using an S.C.R. type control. The photocell control maintains theloop in the vacuum box at a nominal length and the inertia of the unwinddrive system and the mechanism that feeds web to the loop is such thatthe feed motor does not respond to the rapid intermittent variations inloop length resulting from indexing of the draw rolls. A loop sizesensing switch controls the initial size of the loop when starting upthe machine. In one form of the apparatus a flexible opaque shade ridesinside the loop so that the photocell control can operate on transparentweb material.

9 Claims, 6 Drawing Figures CLUTCR-BRAKE,38 INDEXED DRAW l ROLLS,

VACUUM BOX E MAIN DRIVE MOTOR ,33

PATENTEBAPR 30 m4 SHEET 1 OF 5 i m-fi-hil mimsnmao m4 3.307312 SHEET 20F 5 .F'Il3 IE:

4 ARM. FIELD POWER UNWIND ROLLS SUCTION BLOWER,Z4

VACUUM BOX,B as

PATENTEMPRSO m4 3,'807;s12 SHEET 3 OF 5 FIE'| E T 230 AC us 1 START 1 l44 TL 1 T L 2.

MOTOR CONTROLLER A1 A2. F1 F2, I I P 112a ARM.

SHUNT FbEclsD MOTOR m mmmo m4 3.807312 SHEEI h BF 5 TII3 PHENTEDAPN W3.801612 SHEET 5 0F 5 TII3-EI POWER UNWIND ROLLS sucnoN BLOWER,24

VACUUM B0x,B

WEB FEEDING APPARATUS FOR BLANK MAKING MACHINE FIELD OF THE INVENTIONThis invention relates to a machine for cutting blanks from an indexedcontinuous web and more particularly to a web feeding apparatus for sucha machine involving a vacuum box loop device and photocell control forthe web unwinding motor.

DESCRIPTION OF PRIOR ART The use of a double loop, vacuum box withphotocell loop control in a tape recorded feed is shown in the U. S.Pat. to Ferrier Jr. No. 3,563,492, Feb. 16, 1971. The signals from thephotocells, the nature of which are not disclosed, are in effect,neutralized when the loops are at their mid positions.

The U.S. Pat. To Zarleng No. 3,240, 11 1 March 15, 1966 shows a loopcontrol system employing photovoltaic solar cells in parallel andcontrolling a magnetic amplifier. This photo-voltaic system requires acompensating low impedance amplifier to correct for the shunting effectof the cells that are not strongly illuminated during operation of thesystem. Photoresistance cells do not present this problem.

The U.S. Pat. to Klein No. 3,236,429, Feb. 22, 1966,

employs a double loop control for a tape recorder using solar orphoto-voltaic cells to provide a DC voltage when illuminated. Thesecells control logic circuits and two SCR firing circuits in doublebridge circuits for operating the reel motors in conjunction with amotor speed sensing tachometer connected to each reel drive motor.

The U. S. Pat. to Thomas No. 3,129,719 Apr. 21, 1964, shows an acidscaling device for metal bands employing banks of photocells and lightsfor controllingthe loop lengths. The nature of the photocells and of thecontrol circuit is not specifically disclosed.

The U. S. Fat. to Best et al. No. 3,177,749, Apr. 13, 1965, discloses aloop formation device wherein strip steel is withdrawn from the loop ata constantly varying rate and the photocells that sense loop positioncontrol switches in the variable speed drive motor circuit.

The U. S. Pat. to Christian No. 3,721,376, Mar. 20, 1973, shows a stripfeed system wherein a loop is formed and its length is determined by anelongated lamp and a single photocell behind a side angle lens.

Other and less pertinent patents that show loop control systems are theU. S. Pats. to Long No. 3,047,198, July 31, 1962 and Anderman Jr. U.S.Pat. No. 3,277,305, Oct. 4, 1966.

SUMMARY OF THE INVENTION The work feeding apparatus of the presentinvention is employed in a machine for cutting blanks from a strip orweb, which machine includes indexed draw rolls for intermittentlywithdrawing the web from a loop formed in a vacuum box. Photo-resistancephotocell devices are spaced along one side of the vacuum box and lampsare disposed along the other side thereof for sensing the size or lengthof the loop. The photocells trigger a control device of the siliconcontrolled rectifier (SCR) type connected to a variable speed DC motor.A change in the signal from the photocell devices caused by a prolongedchange in the length of the loop during operation of the blank machinetriggers the motor controller to change the speed of the motor andrestore the length of the loop to a predetermined nominal value.However, under the present invention the inertia of the parent roll andof the unwinding roll drive means and other elements feeding the loop isgreat enough so that the unwind motor does not respond to the effects ofintermittent web withdrawal by the indexed draw rolls downstream of theloop and just ahead of the blank forming dies. As mentioned, in order toavoid interaction among the photocell devices the photocells are of thephoto-resistance type and are connected in parallel to the SCR typecontrol.

In order to minimize the effectiveness of the vacuum blower for thevacuum box, adjustable side sealing plates confine the edges of theloop.

A loop size sensing device prevents the formation of an oversize loopwhen first threading the feed apparatus for start up.

In order to make it possible to control the loop when the web materialis transparent or substantially transparent, a flexible shade issuspended from the upper portion of the vacuum box. This shade issubstantially opaque to light and is disposed inside of the loop. Theshade is formed of thin, flexible material for accommodating itself tothe loop configuration and is long enough to always extend to at leastthe bottom of the loop. In this matter the aforesaid photocell controlsystem can be employed for transparent web or strip materials.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a section taken on line 4-4of FIG. 2.. FIG. 5 is a modified form of a vacuum box embodying theopaque shade for use for transparent material.

FIG. 6 is an enlarged fragmentary view of the lower portion of thevacuum box.

BRIEF DESCRIPTION OF THE BLANK FORMING MACHINE The blank forming machineof FIG. 1, which embodies the web feeding apparatus of the presentinvention, has an unwind stand that mounts the parent roll of thinmaterial, such as cardboard, paper, plastic or the like. A continuousweb of material is cut from the parent roll by a strip cutter and isdelivered to powered unwind rolls driven by a variable speed, DC unwindmotor. A loop of material is formed and maintained in a vacuum box at anominal length under the control of photoelectric cells and a controlsystem to be described presently. The vacuum box also mounts a suctionblower to maintain the vacuum therein and thus form the loop into asymmetrical configuration. The machine includes a set of indexed drawrolls which are intermittently rotated or oscillated by a main drivemotor to intermittently feed predetermined lengths of the web to areciprocating die set that includes knives which cut the web intoblanks. The machine also includes trimming, scoring and creasing knives.Except for the vacuum'box and other equipment associated with the webfeed apparatus, the details of the blank making machine of FIG. 1 arenot critical to the present invention. The machine may be of the typeshown in copending application of Eggert et al., Ser. No. 149,302 filedJune 2, 197l and assigned to the FMC Corporation, which application isincorporated herein by reference for a more complete disclosure ofvarious details of the blank making machine shown completely butdiagrammatically in FIG. 1.

Referring more specifically to FIG. 1, the blank forming machineincludes a laterally adjustable unwind stand the shaft of which mounts alarge ,parent roll R of thin cardboard, paper or plastic material. Theunwind stand is laterally positionable on a track structure 1 1. A webor strip W of material is cut from the parent roll by a strip cutter 12and fed through the machine. The roll R may have a diameter of 5 feetand a length of 42", and hence a full roll has a high rotationalinertia. The web W passes over an idler roll 14 and through uncurlingand edge trimming devices indicated generally at l6, the details ofthese not being critical to the present invention. The web is unwoundfrom the parent roll by a pair of power driven unwind rolls 18, drivenby a DC, variable speed unwind motor 22. A loop L of the web material isformed in a vacuum box B to which is connected a suction fan or blower24 driven by a motor 26 for maintaining a partial vacuum in the box andthus arranging the loop in a symmetrical form. In accordance with thepresent invention, a bank of photocells PC is disposed along one side ofthe vacuum box and illumination lamps 28 are disposed along the otherside of the box.

After leaving the vacuum box, the web is trained around an idler roil 30and is intermittently advanced by indexed draw rolls 31 which presentthe web to a vertically reciprocating die set 32, the web feed beinginterrupted sufficiently along for the dies to close and form theblanks. As described in the aforesaid Eggert application, a main drivemotor 33 operates the draw rolls 31, the die set 32 and other points ofthe blank forming apparatus, most details of which are not critical tothe inventionand which need not be described in order that the inventionbe understood. Briefly, however, the motor 33 drives a jackshaft 35which operates a gearbox 36.'The latter operates an oscillatingmechanism 37 that indexes the draw rolls 31 through a clutch brake 38,the clutch-brake being controlled by a cam operated switch (not shown)driven by the gear box 36. Thus when the clutch-brake 38 is on clutchthe draw rolls are indexed through a cog belt and pulley drive whereaswhen the clutch-brake is on brake" the draw rolls are held by the brakeand the clutch is disengaged, which permits free retraction oroscillation of the mechanism 37. The jackshaft 35 also drives a gear box39 through a clutch-brake (not shown) to cause reciprocation of theupper die of the die set 32. Control for starting and stopping operationof the draw rolls 31 and the die set 32 is separate and independent ofthe control for the web unwind motor 22.

As previously mentioned the aforesaid application of Eggert et al., Ser.No. 149,302 discloses a suitable strip cutter 12, the mechanism 36, 37for operating the draw rolls 31 and the die set 32 from the main drivemotor 33, the clutch-brakes and their controis, as well as details ofother portions of the blank forming apparatus which need not bedescribed herein in order that the present invention be clearlyunderstood.

VACUUM BOX ASSEMBLY FIGS. 2 and 4 illustrate details of the preferredinstruction of the vacuum box assembly B and associated elements.

The assembly is mounted on a frame structure for the apparatusillustratd generally at 40, and includes two upstanding side plates 42,between which various rolls and the vacuum box are disposed. Thedirection changing roll 14, previously mentioned, is mounted at theupper portion of the side plates 42, as seen in FIG. 2. As is also seenin FIG. 2 the decurling and trimming knife units referred to generallyat 16, include a decurling or straightening roller 44 and an edgetrimming cutter 46 that cooperates with the back up roll 48 for trimminga narrow strip 49 from one edge of the web W, which strip dischargesinto a tube 50, it being understood that this trimming apparatus is notcritical to the present invention. The upper power unwind roll 18, whichis rubber covered, is also mounted between the side plates 42 as is thelower unwind pinch roller 20, this roller being spring urged against theupper roller 18 by two arms 52 pivoted to the side plates 42 and raisedby springs 54, only one arm 52 appearing in FIG. 2.

The DC unwind motor 22, previously described, drives into a gearreduction box 56, the details of which are not critical to the presentinvention. The output shaft 57 of the gear reduction box 56 drives asmall sprocket 58, a chain 60 and a sprocket 62 for the shaft 63 of theupper power unwind roll 18, all as seen in FIG. 2. The chain 60 passesover idlers 64, 64a, one of which may be adjustable in accordance withthe conventional practice.

The direction changing roller 30, previously de scribed, is mountedbetween brackets 65 associated with the side plates 42, it beingrecalled that the web W is intermittently withdrawn over the roller 30from the loop L of web material by the indexed draw rolls 31 shown inFIG. 1.

The vacuum box is characterized, in its preferred embodiment, as adouble wall, generally cylindrical box having inner and outer shells 70,80 closed by fixed side plates and having a throat or opening at theupper portion thereof for receiving and paying out web material from theloop L. At least the inner wall or shell of the vacuum box iscylindrical to nicely accommodate an expanded or ballooned loop L, whichloop is shaped by drawing a vacuum through a row of opertures formed inthe inner shell and disposed at the midportion or midplane of the vacuumbox. In order to augment the vacuum action, opposed circular sidesealing plates are slidably mounted to laterally confine the loop L andto seal against the inner shell, it being understood that the width ofthe loop L is usually considerably less than the axial length or widthof the vacuum box B. The photocells PC and their illuminating lamps 28,previously described, are mounted on opposed walls of the inner shell ofthe vacuum box.

The details of the vacuum box will be described more specifically inconnection with FIGS. 2 and 4. An entrance throat for the loop of webmaterial is formed by extending the upper web receiving end of the innershell 70 to form a curved guide 74 which terminates at the delivery sideof the unwind rolls 18, 20. The other edge of the inner shell 70terminates in a shorter lip 76 which delivers the web from the loop Lsmoothly to the direction changing roller 30, previously described.

The inner shell 70 of the vacuum box is surrounded by the outer shell80, and in order to save space and reduce the clearance volume and outershell 80 generally conforms to the inner shell 70, as seen in FIG. 2.The two upper ends or edges 82, 84 of the outer shell 80 are welded tothe inner shell 70 adjacent the inlet and exit throat of the latter. Inorder to mount the suction blower 24 the outer shell 80 has a verticalwall 86 (FIG. 2) which merges with a lower, tangential all 88 and theinlet duct 90 of the blower 24 fits snugly in an opening formed in thevertical wall 86 of the outer shell.

As seen in FIG. 4, in order to provide an air-tight chamber between theouter shell and the perforated inner shell 70, side plates 90, 92 arewelded to the end edges of both shells and also enclose the space withinthe inner shell 70.

Mention has been made of side sealing plates within the inner shell 70which loosely confine the loop L and maximize the effect of the vacuumdrawn by the blower 24 in forming or arranging the loop L. The sealingplates just mentioned are of identical const-uction and hence are givenidentical reference characters 94. Each sealing plate 94 is supported,cantilever fashion, on a rod 96 which extends through opposed apertures98 in the slide plates 90, 92. Each of the rods 96 is slidably supportedin a large bushing 100 bolted to the side plates 42 previouslydescribed. In order to exclude the entry of air around the rods 96, feltseals 102 are provided in each bushing 100 as seen at the left of FIG.4. The differential pressure on the side sealing plates 94 caused bypulling a vacuum through the apertures 72 in the inner shell 70 by thesuction blower 24 urges the plates 94 toward the midportion of thevacuum box. Thus the sealing plates 94 must be firmly positioned intheir adjusted relation to the loop L, and this is accomplished by meansof collar 104 on each of the rods 96 which collars can be secured to therods by set screws or the like at the adjusted positions of the plates94.

In order to further improve the efficiency of the suction action of theblower 94 on the loop L, each ofthe side sealing plates 94 mounts aperipheral felt washer 106 which is mounted or clamped on the plate 94by an annulus 107-, the details of the clamp structure not beingcritical to the present invention. The felt washers 106 make sliding,sealing engagement with the inner wall of the inner shell 70 whichaugments the ballooning action of the differential pressure of the loopL, which pressure is the difference between subatmospheric pressure onthe outside of the loop, caused by the suction blower 24, and theatmospheric pressure on the inside of the loop. This causes the loop toassume a generally smooth, circular configuration as shown, for example,in FIG. 2.

In accordance with the present invention the speed of the DC unwindmotor 22 is controlled by the photocells PC under illumination of thelamps 28 (FIG. 2) previously described. In the present embodiment, thereare four photocells PC mounted behind apertures formed in the innershell 70. Of course, access plates (not shown) can be provided on theouter shell 80 at the photocells to facilitate wiring, mounting andreplacement, this being a mere mechanical detail not critical to thepresent invention.

It has been found that three of the lamps 28 which are also mountedbehind apertures formed in the inner.

shell are adequate with the size apparatus under description. The lamps28 are normally 12 volt lamps rated at 0.15 amperes. The manner in whichthe photocell-lamp assembly just described controls the DC unwind motor22 will be described presently.

LOOP SWITCH In order to insure that a full loop is in the vacuum box Bbefore the draw rolls 31 and the die set 32 are started up to withdrawweb and make blanks, a mechanically actuated loop switch 108 isprovided. In the illustrated embodiment, this is a normally closedswitch that is opened by depression of a blade 109 that projects intothe vacuum box B through an opening in the inner shell 70. Duringnormalblank making operation with a loop L present in the vacuum box,the loop control system controls the speed of the unwind motor 22 sothat the loop does not engage the blade 109 and the switch 108 remainsclosed, which places control of the unwind motor 22 under the automaticphotocell and controller system.

The loop switch 108 functions primarily when first threading andstarting up the web feed apparatus, and before the draw rolls and dieset are started up. When the web W is first threaded through the unwindrolls 18, 20, down into the vacuum box B and out over the roll 30, theloop L will ordinarily be too short to reach the switch blade 109. Whenthe unwind motor 22 is turned on, since the loop is short, the photocellcontrol mechanism will cause web feeding by the unwind motor 22 toincrease the length of the loop. However, even when the loop reaches theposition shown at L1 in FIG. 2, thereby eclipsing the lowermostphotocell PC, the nature of the motor controller employed is such thatthe unwind motor 22 is not brought to a dead stop. Thus the unwind motorcontinues to creep" slowly, and hence will feed and enlarge the loopuntil it engages the blade 109 and opens the switch 108. This turns offall power to the motor controller and hence to the unwind motor 22, andno more web material will be fed into the vacuum box B until the drawrolls 31 (FIG. I) and the die set 32 are started up. The first indexingof the draw 'rolls withdraws enough of the material from the vacuum boxso that the loop L clears the switch blade 109, which reopens the switch108 and restores control of the unwind motor to the photocell circuit.Of course, during blank machine operation the average rate of webwithdrawal by the draw rolls greatly exceeds the creep speed of theunwind motor when all photocells in the control system are eclipsed, sothat loop control is provided by the photocell system.

LOOP CONTROL CIRCUIT The control circuit employed in the presentinvention for maintaining the loop at its normal length during normaloperation of the machine is illustrated diagrammatically in FIG. 3. Eachof the photocells PC is of the photoresistance type (also referred to inthe art as the photoconductive type) in that the resistance (the inverseof the conductance) of the light sensitive material in the cell changesas the intensity of the light impinging upon the material changes. Inthe embodiment of the invention being described, the resistance of thephotocells isat a maximum when they are dark and decreases as they areilluminated or stated differently, the conductance of the photocells isat a minimum when they are dark, and increases when they areilluminated.

The cells employed in the embodiment being described are Clairex cellsof the CL-SM series and specifically are type CL-M4L. These cells aremanufactured by Clairex Electronics, a division of Clairex Corporationat 560 South Third Avenue, Mt. Vernon, N.Y., and they are described indata sheets l04JITO8-7O issued by the aforesaid supplier.

These cells include Type 4CdSe sensitive material and have a resistanceat two foot candle illumination of about 025K ohms and a minimum darkresistance in the order of 167K ohms.

As seen in FIG. 3, the four photocells PC are wired in parallel acrosslines leading to terminals T 126 and T 28 of a motor controller 114.This controller operates on small variations of an internally suppliedDC voltage caused by changes in the effective resistance of the bank ofphotocells, thus providing signal voltages that are a function of thecombined resistance of all photocells PC, illuminated or dark.

The controller 1 14 is of the type wherein these signal voltages areapplied to internal operational amplifiers which in turn operate solidstate trigger transistors which gate solid state power devices of thesilicon controlled rectifier (SCR) type. These, in turn, control thecurrent directed to the armature of the DC motor 22 by outputs fromcontroller terminals Al, A2 on the motor controller.

In the embodiment being described the motor 22 is of the shunt fieldtype and its field terminals are connected to the terminals F1, F2 ofthe controller for provlding a feedback type speed control.

The motor controller 114 is powered from a 230 volt AC line throughremote control relay contacts 112a, 112b entering terminals TLl, TL2 ofthe controller. The basic or nominal speed level of the unwind motor 22is adjusted by rheostat 110, which corresponds to and replaces a speedcontrol potentiometer supplied with the controller. The line leading tothe terminal T 28 of the controller and including the rheostat 110 alsoincludes a set of remote control relay contacts 1 120 for turning theunit on and off in a conventional manner. The lamps 28 arefed from thepower line through a transformer 116 which reduces the voltage to thenominal lamp rating of the twelve volts AC.

It is not necessary. to describe the circuitry of the motor controller114 in detail, inasmuch as devices of this general nature are availableto the trade. The device described above is a MinPak V*S Drive for 3 Hpmotor.'These devices are supplied by the Reliance Electric Company,24701 Euclid Avenue, Cleveland, Ohio 44117. The circuit for the deviceunder description is found in the MinPak Instruction Manual D- 3696-2published Nov. 1972 by Reliance Electric and appears on page 11 of thatpublication. It is to be understood that under the broader aspects ofthe invention, a permanent magnet type DC motorcould be employed inplace of the shunt field DC- motor which is illustrated in the circuitdiagram of FIG. 3.

OPERATION OF THE LOOP CONTROL CIRCUIT It will be assumed that the normallength of the loop L is that shown in solid lines in FIG. 2,which'length can be set by adjusting the rheostat 110 shown in FIG. 3.Under these conditions, the lower photocell PC is directly illuminatedby a lamp 28 and the rest of the photocells are eclipsed by the loop.The unwind motor 22 will now run at its predetermined or standard"speed.

With circuit and controller just described, if the average rate of webwithdrawal by the indexed draw rolls 31 (FIG. 1) is less than the presetspeed of the unwind motor 22 (FIG. 2) the loop L will slowly grow orincrease in length until at position Ll, direct illumination of allphotocells PC by the lamps 28 is at a minimum, the photocells arerelatively dark, their net resistance is at a maximum, and theproportion of the internal DC control voltages applied to the internalamplifiers in the controller 114 is at a minimum. This causes the unwindmotor to run at a reduced speed from that determined by the setting ofthe rheostat 110, until the loop length is restored to position L. Therate of operation of the unwind roll 18 by the unwind motor should nowmatch the rate of loop withdrawal by the draw rolls 31.

If the loop becomes short enough for more of the photocells to bedirectly illuminated by a lamp, as at position L2, a second photocell PCis directly illuminated, thereby decreasing the net resistance of thebank of parallel wired cells. This decreases the net re- .sistance ofthe photocell bank, which increases the speed of the unwind motorsufficiently to restore the loop to its normal L position of FIG. 2,thereby permitting the unwind motor to catch up with the increased rateof web withdrawal by the draw rolls 31 which caused this loop condition.

It will be noted that the above description of how the loop controlsystem matches (in effect) the speed of the unwind motor 22 with theaverage rate of web withdrawal by the draw rolls 31 has ignored the factthat in reality, the loop L is being momentarily shortened at a ratethat corresponds to the formation of about 60 215 blanks per minute bythe blank machine. This is explained by the fact that the frequency ofweb with drawal by the indexed draw rolls 31 is much higher than theresponse frequency of the over all web feed apparatus. In other words,although the controller 114 may apply an instantaneous speed up signalto the unwind motor 22 with each indexing of the draw rolls 31, theinertia of the motor 22, that of the associated gearing 56 and that ofthe parent roll of material R is great enough to inhibit instantaneousresponse of the web unwinding system to the rapid, cyclical loopshortening produced by the indexed draw rolls 31. Thus, although the webfeed and loop control system is precisely sensitive to a prolongedmismatch between the effective speed of the unwind motor 22 and theaverage rate of web withdrawal from the loop by the draw roll, it is notresponsive to the above mentioned rapid cyclical decreases in looplength. Stated differently, when operating at its normal or setconditions, over a given period of time the unwind motor 22 and theunwind rolls 18, 20 will supply exactly the amount of web material tothe loop L that is withdrawn by a corresponding number of indexingcycles of the draw rolls 31, and any effective variations in the speedof the unwind motor will only be those required to correct prolongeddifferences between the rate of unwind and the average rate of webwithdrawal by the draw rolls.

LOOP SWITCH CIRCUIT As previously mentioned, the blade operated switch108 is disposed near the bottom of the vacuum box for providing anauxiliary control, assuring that a full loop will be fed into the boxbefore the blank machine proper is started up and without providinginitial over feeding, folding up, creasing, etc. of the loop itself.This blade switch arrangement also makes it unnecessary to providewindows of other means for observing the condition of the loop insidethe vacuum box when first threading or starting up the machine. It alsoinsures that an oversized loop will not be developed. Of course, thephotocell circuit and the motor controller of 114 previously describedmaintain a nominal sized loop in the vacuum box during normal operationof the draw rolls and die set of the machine.

The circuit for the blade actuated switch 108 also appears in FIG. 3. Inthe embodiment of the invention being described this is a normallyclosed switch across the 230 volt line in series with a relay coil 112which operates the normally open contacts 112a, 1121) in the power lineto the controller as well as the normally open contact 112C in one ofthe control lines from the photocells. A manually operated start-stopswitch 115 is also positioned in the 230 volt power line ahead of all ofthe circuit elements of the web control system. The circuit conditionsillustrated in FIG. 3 are those wherein the loop L clears the blade 109of the switch 108 and since the switch 108, in the present embodiment,is a normally closed switch, the relay coil 112 will then be energized.This means that the normally open contacts 112a, l12b and 112C are allclosed and hence the unwind motor 22 is under control of the photocell,lamp and controller system.

As previously mentiond, when initially threading the web materialthrough the machine and into the vacuum box to form the loop, the loopwill be short and the regular automatic control system with the contacts112a, b and c closed as illustrated in FIG. 3, will energize the unwindmotor 22 and cause development of a loop. As previously explained, sincethere is a small creep" of the unwind motor 22 under control of an SCRtype control 114 previously described, even when all of the photocellsPC become eclipsed by the loop, the unwind motor is not completelydeenergized, but slowly continues to feed material into the vacuum boxand hence enlarge the loop, so long as no web material is beingwithdrawn from the loop by the indexed draw rolls 31. Thus, even thoughthe photocells PC are all eclipsed, the loop will gradually enlarge dueto the aforesaid creep of the unwind motor, until the loop engages theswitch blade 109 thereby opening the normally closed loop sensing switch108. This deenergizes the coil of relay 112 (which was holding controls112a, 1121; and 1120 closed) and thereby permits the normally opencontacts 1120, 112b and 112s to open. Opening of the contacts 112a and 112b shuts off all power to the motor controller and hence brings theunwind motor 22 from its slow or creep operation to a dead stop. Theloop, which is fully developed but is not developed enough to causecreeping and folding, is now ready for withdrawal of web material uponsubsequent starting up of the blank forming machine elements, includingthe operation of the indexed draw rolls 31. Upon the first indexing ofthe draw rolls 31, enough web material is withdrawn from the vacuum boxto shorten the loop L sufficiently to clear the switch blade 109. Thisrecloses the switch 108, re-energizes the relay 112 and recloses thecontacts 112a, ll2b and l12c. The automatic control system is nowenergized for automatic operation, which condition is shown in thediagram of FIG. 3.

TRANSPARENT MATERIAL CONTROL FIG. 5 is a view like FIG. 2 showing amodified form of the invention employed for controlling the loop lengthwhen the web W is formed of a transparent material such as a plastic orthe like. When the material of the web W is substantially transparent oreven translucent to a certain degree, the loop control system embodyingthe lamps 28 and the photocells PC is rendered either inefficient,inprecise or ineffective. In order to correct this condition, an opaqueshade 120 of thin flexible material is suspended inside of the loop L.The shade is secured to and suspended from a rod 122 which extendsbetween the side brackets of the machine. However, the width of theshade 120 is considerably less than the complete axial extent of thevacuum box. The shade need only be wide enough the eclipse thephotocells PC from the lamps 28 and hence can have a maximum width thatis only somewhat less than the narrowest strip of web material W that isdrawn through the vacuum box. The length of the shade 120 is adequate toreach the bottom of the loop and hence eclipse the lowermost photocellPC when the loop is enlarged enough to receive light reachingthelowermost photocell. The differential air pressure across the looppreviously described, causes the shade 120 to substantially conform tothe interior surface of the loop, and being formed of thin, flexiblematerial the shade 120 does not interfere with the provision of asmooth, substantially symmetrical loop configuration.

In both modifications of the invention previously described, it is to beunderstood that the unwind stand 10 (FIG. 1) is, in accordance withconventional practice, moveable axially or laterally across the blankforming machine. Thus in operation, the unwind stand 10 is positionedrelative to the remainder of the machine so that the web or strip W ofmaterial removed by the strip cutter 12 from the parent roll R iscentered or at least substantially centered relative to the vacuum boxB. Thus, the lamps 28 and the photocells PC are also axially centeredalong the inner shell of the vacuum box which means that they will, ineffect, be substantially aligned with the row of vacuum aperature 72(FIG. 4) formed in the inner shell. With this construction, the loop L,shaded or unshaded will always be interposed between the lamps and thephotocells.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

What is claimed is:

1. Web feeding apparatus of the type comprising an unwind reel, rollmeans for unwinding the web from said reel, variable speed DC. motormeans for continuously driving said roll means, a vacuum box connectedto a vacuum source for accommodating a take-up loop in said web, webfeed means for withdrawing the web from said vacuum box, a bank ofphotocell devices spaced along one side of said vacuum box and lampsalong the other side for sensing the size of said loop, and automaticcontrol means connected to said photocell devices and to said variablespeed motor means for maintaining the length of said loop atsubstantially a predetermined value; the improvement wherein saidfeeding apparatus is employed in a machine for cuttingblanks from theweb and the blank machine includes indexed draw rolls for intermittentlywithdrawing the web from said vacuum box, said control means comprisinga silicon controlled rectifier type D.C. motor controller that istriggered in accordance with the total illumination of said bank ofphotocell devices, a change in the signal from said bank of photocelldevices caused by a prolonged change in the length of said looptriggering said motor controller to change the speed of said motor meansand restore the length of the loop to said predetermined value, theinertia of said unwinding roll drive means being such that said motormeans does not substantially respond to the effects of intermittent webwithdrawal.

2. The web feeding apparatus of claim 1, wherein said photocell devicesare of the photoresistance type and are connected in parallel.

3. The web feeding apparatus of claim 1, wherein the dark resistance ofeach of said photocell devices exalong the other side for sensing thesize of said loop, and automatic control means connected to saidphotocell devices and to said variable speed motor means for maintainingthe length of said .loop at substantially a predetermined value; theimprovement for use when the web is substantially transparent to lightcomprising a substantially opaque shade disposed within said loop, saidshade being formed of thin, flexible material for accommodating itselfto the loop configuration, and means for suspending said shade withinsaid loop from an upper portion of said vacuum box.

5. Web feeding apparatus of the type comprising an unwind reel, rollmeans for unwinding the web from said reel, variable speed motor meansfor driving said roll means,- a vacuum box connected to a vacuum sourcefor accommodating a take up loop in said web, web feed means forwithdrawing the web from said vacuum box, photocell means spaced alongone side of said vacuum box and lamp means along the other side forsensing the size of said loop, and automatic control means connected tosaid photocell means and to said variable speed motor for maintainingthe length of said loop at substantiallya predetermined value; theimprovement wherein said vacuum box comprises an outer shell, a tubularinner shell having an upper loop receiving throat, side plates joiningsaid shells, axially adjustable, loop confining sealing plates slidablymounted within said inner shell, a row of apertures formed substantiallyat the mid portion of said inner shell, and a vacuum blower connectionto substantially a mid portion of said outer shell.

6. The apparatus of claim 5, wherein said inner shell is substantiallycylindrical, said sealing plates are generally circular, and peripheralsealing means on said sealing plates engaging said inner shell.

7. The apparatus of claim 6, comprising a central rod projectinglaterally outwardly from each sealing plate and through an aperture inthe associated vacuum box side plate for facilitating lateral adjustmentof the sealing plates to confine the loop of material.

8. Web feeding apparatus of the type comprising an unwind reel, rollmeans for unwinding the web from said reel, variable speed motor meansfor driving said roll means, a vacuum box connected to a vacuum sourcefor accommodating a take up loop in said web, intermittent web feedmeans for withdrawing the web from said vacuum box, a bank of photocelldevices spaced along one side of said vacuum box and lamps along theother side for sensing the size of said loop, and automatic controlmeans connected to said photo cell devices and to said variable speedmotor means for maintaining the length of said loop at substantially apredetermined value; the improvement comprising loop sensing means fordetecting a loop size larger than that which eclipses all of thephotocells, and auxiliary control means connected to said loop sensingmeans for deenergizing said motor when said large size loop is detected,said auxiliary control means restoring control of said motor to saidautomatic control means upon withdrawal of a length of web from saidvacuum box by said intermittent web feed means.

9. The apparatus of claim 8, wherein said auxiliary control meanscomprises a switch for causing deenergization of said motor and saidloop size sensing means comprises an actuator for said switch projectinginto the vacuum box, actuation of said switch actuator by a large sizeloop operating said switch to deenergizing said motor until the loop iswithdrawn from said actuator by the intermittent web feed means.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 807, 2

DArED April 30, 1974 INVENTORU) RALPH H. EGGERT It is certified thaterror appears in the above-idenlrfied patent and that said LettersPatent G are hereby corrected as shown below:

Column 1, line 14, "recorded" should be -recorder-.

Column 1, line 19, "'To should be -to-.

. Column 1, line 48, "side" should be --wide--.

Column 2, line 13, "minimize" should be -maximize-.

Column 3, line 42, "points" should be -portions-.,

' Column 4, line 9, "illustratd" should be --illustrated-. Column 5,line 11, "all" should be --w a11--'.

Column 7, line 45, delete "the".

Column 8, line 51, "average" should be underlined.

Column 9, line 31, "mentiond" should be --mentioned.'

Column 9, line 57, "creeping" should be --creasing-.

O Column 10, line 17, "the" (second occurrence) should be Column 11,line 27, "bank" should be --b0x--.

Column ll, line 49, after motor" add ---means----.

Column 12, line [p6 "deenergizing" should be -deenergiz 'igncd andScaled this eighteenth D3) Or November 197- [SEAL] Arres'r:

RUTH c. MASON c. MARSHALL DANN ('nnmusximu'r u] Iarvnrs and Trademark

1. Web feeding apparatus of the type comprising an unwind reel, rollmeans for unwinding the web from said reel, variable speed D.C. motormeans for continuously driving said roll means, a vacuum box conneCtedto a vacuum source for accommodating a takeup loop in said web, web feedmeans for withdrawing the web from said vacuum box, a bank of photocelldevices spaced along one side of said vacuum box and lamps along theother side for sensing the size of said loop, and automatic controlmeans connected to said photocell devices and to said variable speedmotor means for maintaining the length of said loop at substantially apredetermined value; the improvement wherein said feeding apparatus isemployed in a machine for cutting blanks from the web and the blankmachine includes indexed draw rolls for intermittently withdrawing theweb from said vacuum box, said control means comprising a siliconcontrolled rectifier type D.C. motor controller that is triggered inaccordance with the total illumination of said bank of photocelldevices, a change in the signal from said bank of photocell devicescaused by a prolonged change in the length of said loop triggering saidmotor controller to change the speed of said motor means and restore thelength of the loop to said predetermined value, the inertia of saidunwinding roll drive means being such that said motor means does notsubstantially respond to the effects of intermittent web withdrawal. 2.The web feeding apparatus of claim 1, wherein said photocell devices areof the photoresistance type and are connected in parallel.
 3. The webfeeding apparatus of claim 1, wherein the dark resistance of each ofsaid photocell devices exceeds its resistance when illuminated by alamp.
 4. Web feeding apparatus of the type comprising an unwind reel,roll means for unwinding the web from said reel, variable speed motormeans for driving said roll means, a vacuum box connected to a vacuumsource for accommodating a take up loop in said web, intermittent webfeed means for withdrawing the web from said vacuum box, a bank ofphotocell devices spaced along one side of said vacuum bank and lampsalong the other side for sensing the size of said loop, and automaticcontrol means connected to said photocell devices and to said variablespeed motor means for maintaining the length of said loop atsubstantially a predetermined value; the improvement for use when theweb is substantially transparent to light comprising a substantiallyopaque shade disposed within said loop, said shade being formed of thin,flexible material for accommodating itself to the loop configuration,and means for suspending said shade within said loop from an upperportion of said vacuum box.
 5. Web feeding apparatus of the typecomprising an unwind reel, roll means for unwinding the web from saidreel, variable speed motor means for driving said roll means, a vacuumbox connected to a vacuum source for accommodating a take up loop insaid web, web feed means for withdrawing the web from said vacuum box,photocell means spaced along one side of said vacuum box and lamp meansalong the other side for sensing the size of said loop, and automaticcontrol means connected to said photocell means and to said variablespeed motor for maintaining the length of said loop at substantially apredetermined value; the improvement wherein said vacuum box comprisesan outer shell, a tubular inner shell having an upper loop receivingthroat, side plates joining said shells, axially adjustable, loopconfining sealing plates slidably mounted within said inner shell, a rowof apertures formed substantially at the mid portion of said innershell, and a vacuum blower connection to substantially a mid portion ofsaid outer shell.
 6. The apparatus of claim 5, wherein said inner shellis substantially cylindrical, said sealing plates are generallycircular, and peripheral sealing means on said sealing plates engagingsaid inner shell.
 7. The apparatus of claim 6, comprising a central rodprojecting laterally outwardly from each sealing plate and through anaperture in the associated vacuum box side plate for facilitatinglateral adjustment of the sealing plates to confine the loop ofmatErial.
 8. Web feeding apparatus of the type comprising an unwindreel, roll means for unwinding the web from said reel, variable speedmotor means for driving said roll means, a vacuum box connected to avacuum source for accommodating a take up loop in said web, intermittentweb feed means for withdrawing the web from said vacuum box, a bank ofphotocell devices spaced along one side of said vacuum box and lampsalong the other side for sensing the size of said loop, and automaticcontrol means connected to said photocell devices and to said variablespeed motor means for maintaining the length of said loop atsubstantially a predetermined value; the improvement comprising loopsensing means for detecting a loop size larger than that which eclipsesall of the photocells, and auxiliary control means connected to saidloop sensing means for deenergizing said motor when said large size loopis detected, said auxiliary control means restoring control of saidmotor to said automatic control means upon withdrawal of a length of webfrom said vacuum box by said intermittent web feed means.
 9. Theapparatus of claim 8, wherein said auxiliary control means comprises aswitch for causing deenergization of said motor and said loop sizesensing means comprises an actuator for said switch projecting into thevacuum box, actuation of said switch actuator by a large size loopoperating said switch to deenergizing said motor until the loop iswithdrawn from said actuator by the intermittent web feed means.